Evaluation of insulin lispro and biosynthetic human insulin in pulmonary absorption: in vivo and in vitro studies.

OBJECTIVE To compare the pulmonary absorption characteristics of two insulin solutions-humalog (insulin lispro) and Novolin R (Biosynthetic Human insulin) with in vivo and in vitro methods. METHODS Investigate the pharmacodynamics in Sprague Dawley (SD) rat model (in vivo studies) and permeability across Rana catesbeiana pulmonary membrane (in vitro studies) of Biosynthetic Human insulin (BHI) and insulin lispro (LI) at different doses. RESULTS Both of the insulins could reduce blood glucose levels promptly after pulmonary administration. But LI showed a better tendency on hypoglycemic effect than BHI in the in vivo studies. In the in vitro studies, the apparent permeability coefficient (Papp) for BHI and LI were almost constant with increasing concentrations, which implied that insulin maybe passively diffuse through the Rana catesbeiana pulmonary membrane barrier. Interestingly, the Papp of LI was obviously higher than that of BHI, indicating that the permeability of LI across Rana catesbeiana pulmonary membrane was more effective than that of BHI. CONCLUSION These in vitro and in vivo results suggested that LI was easier to be absorbed in the lung than BHI and Rana catesbeiana pulmonary membrane had a potential ability, as a transport model, to predict in vivo pulmonary absorption of insulin.